Cytoskeleton

The cytoskeleton is essential for the movement and regulation of cells. They are formed by the combination of actin filaments, microtubules, and intermediate filaments. They provide a stable structure and size to the cells and maintain the organelles of the cells. Furthermore, they also support the cell division process. Let us learn more about the cytoskeleton and its components.

Eukaryotic cells (nucleus membrane containing) have a system consisting of filaments and fibres embedded in the cytoplasm. That system is known as the cytoskeleton. 

The cytoskeleton system supports the regular functioning and maintenance of constituents present in the cell. It also regulates the shape of cells and is responsible for the locomotor movements of cells and other organelles present in them. 

Filaments 

The filaments are tiny structures. They are made up of proteins and give biomechanical support to the cell and other organelles. The cytoskeleton also supports other functions of cells such as differentiation, division and mobility. The cytoskeletal structure is made up of more than one ingredient. Every type of cytoskeleton has three main classes of constituents but differ in size and protein composition.

The types of filaments 

• Actin filament 
• Microtubules
• Intermediate filaments 

Actin filaments 

They are the smallest in structure, have a diameter of about 6 nm, and comprise the protein known as actin. They are present in the cell body in the bundle form, and fibres are arranged in a parallel manner. 

They characterise the shape and size of the cell body and support the attachment system to link with substrates. Furthermore, they also control the mobility of cells and organise certain activities in the cell, like, cell cleavage during the process of mitosis. They are found in abundance in the cell body. They are formed by the actin proteins organised in a spiral form.

Microtubules 

They are the longer filaments in the cell. They have a diameter of about 25 nm and comprise a protein known as tubulin. They frequently compile and dismantle throughout the cell and; and play an essential role in mitosis. They support the movement of daughter chromosomes towards the newly produced daughter cells and bunches of microtubules, creating cilia and flagella (commonly found in protozoan and multicellular animals). 

It consists of two polypeptide chains which are linked to creating long strands known as protofilaments. Then, all proto filaments come together and form a hollow and straw-shaped structure of microtubules. 

Intermediate filaments

Unlike actin filaments and microtubules, these filaments are stable which creates the exact skeleton of the cell. They are median size filaments with a diameter of 10 nm. They support the nucleus and fix the position inside the cell. The flexibility of the cell is accomplished by these filaments and enables the cells to prohibit external pressure. They also provide strength to delegate fibres present in the cell body. 

Movement of cells(function) 

The structure of cytoskeletal filaments gives the base for the mobility of cells. For example, cilia and flagella structure help in the movement of cells, and they slide along each other. Even the extension of the structure of microtubules exhibits an organised form of movement. Apart from this, there are other types of cell movements, such as pinching off of membrane during cytokinesis because of the potential nature of actin filament. Actin filaments have a very dynamic nature that forms and disperses rapidly. Moreover, this behaviour helps the movement of amoeba.

Note-

Cilia & Flagella are Mechanical,  hair-like cellular appendages and locomotory structures. The shaft or ciliary part of the flagella is a projecting hair-like part of the ciliary apparatus. Cilium is composed of 11 microtubules. (9 doublets +2 singlet) .Bundles of microtubules are called axonemes. Nine microtubules are peripheral and each composed of two small tubules I, e. A tubule with two atms and B-Tubules without arms. Microtubules consist of contractile protein tubulin similar to the action of muscles. Arms of A tubules consist of enzymatic protein dynein similar to muscle cells. Dynein has the ability to hydrolysis of ATP & liberates energy for ciliary movement.

Conclusion

Mainly eukaryotic cells consist of the cytoskeleton system (combination of fibres and filaments). Furthermore, the cytoskeleton is composed of three different fibres such as actin filaments, microtubules and intermediate filaments. They play a vital role in the movement and regulation of cells. They provide stable structure and size to the cells and maintain the organelles of the cells. Furthermore, they also support the cell division process.